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Test Code LAB908 Gestational 3HR Glucose Tolerance Test

Clinical Information

This test is intended for the diagnosis of gestational diabetes mellitus. The order is intended to be used with a 100 g oral glucose load and is structured in accordance with "Step 2" of the "Two-Step" strategy for diagnosing gestational diabetes mellitus from the American Diabetes Association's clinical practice recommendations. This order includes a fasting glucose sample (fasting defined as no caloric intake for 8 hours), 1 hr-, 2 hr-, and 3 hr- post-100 g oral glucose load samples.

Synonym

  • GTF
  • GT1H
  • GT2H
  • GT3H

Profile Information

Reporting Name Available Separately Always Reported
Glucose Tolerance, Fasting Yes Yes
Glucose Tolerance, 1 Hr No No
Glucose Tolerance, 2 Hr No No
Glucose Tolerance, 3 Hr No No

Specimen Required

Preferred Container/Tube: Mint Green Top
Acceptable Container/Tube: Mint Green Top, Gold SST Top
Specimen Volume: 3 mL
Specimen Minimum Volume: 1 mL

Specimen Stability Information

Ambient: 8 hours
Refrigerated: 3 days

Rejection Due To

  • Gross hemolysis
  • Gross icterus
  • Quantity not sufficient
  • Quality not acceptable

Reference Values

Glucose Tolerance, Fasting
70-94 mg/dL

 

Glucose Tolerance, 1 Hr
70-179 mg/dL

 

Glucose Tolerance, 2 Hr
70-154 mg/dL

 

Glucose Tolerance, 3 Hr
70-139 mg/dL

Interpretation

The upper limits of the reference intervals for each fasting, 1 hour, 2 hour, and 3 hour samples are based on the Carpenter-Coustan criteria. According to the ADA practice recommendations, the diagnosis of GDM is made when at least 2 of the four plasma glucose levels meet or exceed the Carpenter-Coustan criteria, although The American College of Obstetricians and Gynecologists notes that some clinicians choose to use just one elevated value.

Method Description

Photometric rate with hexokinase

Cautions

Falsely elevated glucose results may occur in patients taking Eltrombopag.  In some cases of monoclonal gammopathies (especially Waldenstrom's macroglobulinemia with very high concentrations of IgM), glucose results may be unreliable.

Performing Lab

Clinical Lab UH
Clinical Lab University East
Clinical Lab Martha Morehouse
Clinical Lab Spielman

Day(s) Performed

Monday through Sunday

Report Available

Same day/1 day

Reporting Name

Glucose Tolerance, Fasting
Glucose Tolerance, 1 Hr
Glucose Tolerance 2Hr
Glucose Tolerance 3Hr

CPT Code Information

82951
82952

LOINC Code Information

1558-6
20438-8
20436-2
20437-0